A Fragile Web

A Fragile Web

Article excerpt

Surely one of the most enduring concepts from school biology as that of the food web. The idea of an array of organisms, linked together by their interactions as either predator or prey, has a real elegance to it.

And it's a powerful ecological idea. When you consider the deeper significance of the word 'web', it becomes clear that as in a spider's web, when you start removing strands, the whole becomes weakened, a phenomenon that's increasingly taking place in ecosystems around the world.

The overexploitation of fisheries offer some of the most powerful examples. Predators are often the most influential elements of a food web, and the effect of their removal can be disproportionate to their numbers--and many fish are predatory. On North America's Atlantic coast, for example, overfishing of sharks has led populations of their prey, cow-nosed rays, to boom. They, in turn, have decimated the eastern Atlantic bay scallop beds.

These disproportionately influential organisms are known as keystone species, and there can be few as deserving of the label as the salmon of the Pacific Northwest. …